The answer is (2) higher vapor pressure and weaker intermolecular forces. Propanone has a lower boiling point, so it is more volatile than water. Propanone's vapor pressure is, therefore, higher than that of water at 50 degrees Celsius. Propanone is more volatile due to the fact that the intermolecular forces that hold its molecuels together are not as strong as those that hold together molecules of water. Since the IMFs are weaker, it takes less thermal energy to break individual molecules free of each other.
